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(FT/P2-08) Current Control of Superconducting Coils for Fusion Experimental Facility

T. Ise¹⁾, D. Etou¹⁾, H. Chikaraishi²⁾, S. Takami²⁾, T. Inoue^2)
 
1) Dept. of Electrical Engineering, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan
²⁾ National Institute for Fusion Science, Japan

Abstract.  The LHD (Large Helical Device) has twelve superconducting coils and six dc power supplies, and following specifications are required for its control system; each coil current must be controlled independently, the steady state control error is less than 0.01 % of the reference value, the current settling time for 0.1 % of control error is less than 1 second, and the control system must be robust against turbulence caused by appearance and disappearance of the plasma, parameter errors and external electro-magnetic noises. In this paper, the design and test results of the coil current control system for the LHD are described. The good response and robustness are in the relation of trade off each other. H-infinity controller is one of schemes to guarantee robustness. However, the independent responses of six coils were impossible by the H-infinity controller only. To resolve this problem, we applied a feed-forward control with the H-infinity control. Moreover, the advanced design method of H-infinity controller was applied to guarantee the control performance in the whole operating condition. As a result, good control results were obtained by experiments.

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